It is axiomatic that efficient utilization of water--for agricultural as well as for virtually all other purposes--is desired by most of the world's population. For example, not only is efficient utilization of water essential to obtain optimal crop yields, the efficient utilization of agricultural water is known to impact upon navigable water systems, potable water sources and supplies, water for industrial uses, and water for recreational uses.
It is well known that virtually all plants require a certain quantity of water for proper growth and development.
Drought limits the productivity of virtually all plants.
Moreover, the ability of various plant seedlings to survive drought is currently thought to be influenced by chemical as well as environmental pre-treatments.
In any event, it is also well known--with respect to many plant species--that a significant quantity of water absorbed from soil returns to the atmosphere via plant transpiration. In particular, the loss of water through transpiration may be so undesirable as to limit key metabolic processes associated with plant growth and development.
Optimizing water utilization of plants is thus desirable, particularly if the plant is known to possess a commercial agricultural value.
While placing a physical barrier over plant stomata is known to reduce water lost via transpiration, the procedure is not always desirable.
For example, physical barriers over plant stomata may inhibit certain gas-exchange processes of the plant. It would be much more desirable to enable the plant to use more efficiently the water it receives.
In U.S. Pat. No. 4,645,682 to Elmore there is disclosed a method and composition, said to be able to protect a plant from weather-induced damage. Disclosed is a composition said to comprise an aqueous solution containing a dark-hued vegetable dye, an anti-transpiration agent, an agricultural streptomycin, and complexed mineral micronutrients.
The dye is said to be effective for shading the leaves of a plant from the effects of sunlight. The streptomycin is said to be effective for suppressing growth of certain fungus. The micronutrients are said to be effective for promoting plant growth and function.
The anti-transpiration agent is said to be effective for limiting transpiration of water from the plant. In the sole example of the Elmore patent, aqueous paste wax is disclosed as the anti-transpiration agent; while certain other anti-transpiration agents--i.e. those disclosed in each of the U.S. Pat. Nos. 3,791,839; 3,826,671; and 3,847,641--are incorporated by reference into the Elmore patent.
U.S. Pat. Nos. 3,791,839 and 3,847,641, both to Cushman et al., each disclose wax emulsions which are said to be useful for controlling transpiration in plants.
U.S. Pat. No. 3,826,671 to Petrucco et al. discloses a composition said to be effective for controlling transpiration in plants, the composition comprising a polymer, an emulsifier, and water.
In U.S. Pat. No. 4,671,816 to Bliesener et al. there is disclosed an acetylene compound, said to possess utility for regulating plant growth.
Russian patent document SU 1 282 492 to Kuznetsov et al. discloses 2-methyl-4,6-bis(dimethylaminomethyl)-5-hydroxybenzimidazole hydrochloride, which is said to possess plant growth regulator activity.
In Russian patent document SU 1 098 934 to Smirnov et al. there are disclosed 4-aminomethyl derivatives of 2-methyl-5-hydroxybenzimidazole, which are said to possess plant growth regulator activity.
Russian patent document SU 1 253 559 A1 to Kuznetsov et al. discloses 2-methyl-4-dimethylaminomethyl-5-hydroxybenzimidazole hydrobromide, which is said to possess growth-stimulating activity for coniferous tree species.
In Russian patent document SU 1 470 235 A1 to Vishnevetskaia et al. a method is disclosed for determining the sensitivity of certain genetic families of coniferous tree species to the action of a growth-stimulating preparation. In particular, results obtained for the effect of 2-methyl-4-dimethylaminomethyl-5-hydroxybenzimidazole dihydrochloride on the morphological parameters of pine seedlings are shown.
In a document entitled "Ambiol," Stoljarova et al. disclose a plant growth regulator, said to be an anti-stress anti-oxidant of complex effect, possessing anti-mutagenical and radio-protective properties.
In U.S. Pat. No. 4,943,315 to Schulz et al. there are disclosed formulations which are said to possess utility as agents for reducing transpiration in plants and/or for avoiding impairment to plants caused by heat and dry conditions. Such formulations are said to comprise an acetylene as well as a phenylbenzylurea, each of specified structure.
Through the years, those skilled in the art have shown an interest in maintaining a favorable water balance by applying "anti-transpirant" agents (also called "anti-desiccants") to leaves. Such anti-transpirants typically fall into two recognized categories: the "film-type" and the "metabolic" anti-transpirants. Film-type anti-transpirants form a film on leaves, thereby either blocking stomatal pores, or coating leaf epidermal cells with a water-proof film. Typical film-type anti-transpirants include waxes, wax-oil emulsions, higher alcohols, silicones, plastics, latexes and resins. Metabolic anti-transpirants chemically close stomatal pores. Typical metabolic anti-transpirants include succinic acids, phenylmercuric acetate, hydroxysulfonates, the herbicide atrazine, sodium azide, and phenylhydrazones, as well as carbon cyanide.
Anti-transpirants of these sorts have either exhibited phytotoxic effects or inhibited plant growth, as is discussed and shown by T. T. Kozlowski at pages 155-157 in the text entitled Tree Growth and Environmental Stresses (Univ. of Washington Press, Seattle and London, published 1979).
Unlike known prior-art procedures, the anti-transpiration methods of our invention do not involve application to leaves (otherwise referred to as "foliar treatment"). On the contrary, and as will be shown in examples presented below, improved water-use efficiency and increased biomass of plant species treated with the formulations of this invention have resulted either from treatment of seeds or from application to plant root systems.
It would be beneficial to limit transpiration rates, thereby to foster an increase in carbon gain rates per unit of water transpired, the term also being referred to as water-use efficiency ("WUE").
An increase in water-use efficiency would tend to stimulate plant growth under mild drought conditions.
It is thought that trees with higher "WUE" values would dry out soils more slowly and use less water, and that lower plant transpiration rates would cause an increase in plant growth rates by reducing stress levels in plant leaves.